1. FIELD OF THE INVENTION:
The present invention relates to a push button switch and more particularly to improvement of a push button switch of the type including a key stem displaceable by an operator's hand, a depressing portion fixedly secured to the key stem and a contact portion adapted to be turned on or off by depressing force transmitted from the key stem.
2. DESCRIPTION OF THE PRIOR ART:
In general, to assure that a push button switch of the above-mentioned type usable for key board or the like is produced at a reduced cost it is very important that it is designed as simple as possible with the minimized number of components and it is assembled by way of the reduced number of man-hours.
To facilitate understanding of the present invention it will be helpful that a typical conventional push button switch of the above-mentioned type will be described with reference to FIG. 1 as follows. As will be apparent from the drawing, the conventional push button switch is constructed such that a key stem 2 with a key top 1 fixedly secured thereto is vertically displaceably housed in the switch mounting frame 1, a depressing member 4 molded of elastomeric material and a return spring 5 in the form of a coil spring are arranged in a cavity 2a which is formed in the lower part of the key stem 2 and an upper contact 8a secured to a layer of film 8 and a lower contact 8b secured to a layer film are placed on the base plate 6 with a spacer 7 interposed therebetween. When the key top 2 is depressed by an operator's hand, the upper contact 8a is caused to come in contact with the lower contact 8b whereby electrical communication is established therebetween. To damp bounding sound which will be generated in the event of collision of the key stem 2 against the switch mounting frame 3 during return movement of the key stem 2 an O ring-shaped cushion 9 is fitted onto the key stem 2 at the position located on the shoulder of the latter.
However, it has been pointed out as a drawback with respect to the conventional push button switch that the latter is constructed by a number of components and thereby it is assembled only with a number of man-hours consumed therefor, resulting in production of the push button switch being achieved at an increased cost.